Poisson's ratio

2016-11-09T12:38:46Z

5.151.1.215: Added a full stop and a capital letter to make article clearer - two sentances were running into each other

'''Poisson's ratio''' (letter ''v'') is a measure of the contraction that happens when an object is stretched. This contraction is perpendicular to the stretching force. It can also expand as the object is compressed in a perpendicular direction.
[[Image:PoissonRatio.svg|thumb|300px|right|Figure 1: A cube with sides of length ''L'' of an isotropic linearly elastic material subject to tension along the x axis, with a Poisson's ratio of 0.5. The green cube is unstrained, the red is expanded in the ''x'' direction by <math>\Delta L</math> due to tension, and contracted in the ''y'' and ''z'' directions by <math>\Delta L'</math>.]]
For example, if a block is being stretched as shown in the image to the right, the equation for the poisson's ratio will be:
:<math>\nu = -\frac{d\varepsilon_\mathrm{trans}}{d\varepsilon_\mathrm{axial}} = -\frac{d\varepsilon_\mathrm{y}}{d\varepsilon_\mathrm{x}}= -\frac{d\varepsilon_\mathrm{z}}{d\varepsilon_\mathrm{x}} </math>
Poisson's ratio ranges from 0.0-0.5 for common materials, though for materials with certain structures, can be as low as -1. A material with a Poisson's ratio close to 0 (like [[cork (material)|cork]]) can be stretched a lot in the axial direction without changing much at all in the transverse, where as pulling on a material with a high Poisson's ratio (like [[rubber]]) will cause it to become much more narrow. A material with a negative Poisson's ratio will expand in all directions as it is stretched.

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[[Category:Physics]]

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Poisson's ratio